1. Field of the Invention
The present invention relates to tapered roller bearings.
2. Description of the Related Art
As shown in FIG. 16, a tapered roller bearing 90 includes an inner ring 91, an outer ring 93, a plurality of tapered rollers 95, and an annular cage 96. The inner ring 91 has a tapered inner ring raceway surface 92. The outer ring 93 has a tapered outer ring raceway surface 94. The tapered rollers 95 roll on the inner ring raceway surface 92 and the outer ring raceway surface 94. The cage 96 retains the tapered rollers 95 at intervals in the circumferential direction. The inner ring 91 has a cone back face rib (hereinafter referred to as a large rib) 97 formed on the larger diameter side of the inner ring 91 so as to protrude outward in the radial direction. The large rib 97 has an annular rib face 99 that contacts large end faces 98 of the tapered rollers 95.
When the tapered roller bearing 90 is rotated, the tapered rollers 95 roll on the raceway surfaces 92, 94, and the large end faces 98 of the tapered rollers 95 slidingly contact the rib face 99 of the inner ring 91. A tapered roller bearing is developed in which the large end faces 98 are convex surfaces having a predetermined curvature radius and the rib face 99 is a concave surface having a predetermined curvature radius in order to reduce friction resistance (sliding friction resistance) between the large end faces 98 and the rib face 99 (see, e.g., Japanese Utility Model Application Publication No. H05-75520).
A common method to reduce the friction resistance between the large end faces 98 of the tapered rollers 95 and the rib face 99 of the inner ring 91 is to reduce particularly the surface roughness of the rib face 99. Conventionally, the rib face 99 is therefore super-finished, lapped, etc. after being ground.
However, since the rib face 99 is a concave surface as described above and is an annular face located inside a recess of the inner ring 91, it is difficult to perform super finishing (or lapping) etc. on such a rib face 99 due to its shape. This is one of the factors that increase manufacturing cost.